Telephone system



Nov. 4 9 1924- L. D. KELLOGG TELEPHONE SYSTEM Filed Jan. 30, 1922 2 Sheets-Sheet 1 151.7227 UP. ZFPQZJZK' E] [174117 Nov. 4 1924. 1,513,825

L. D. KELLOGG TELEPHONE SYSTEM Filed Jan. I50, I922 2 Sheets-Shea! 2 IIHI- ZerayflffeZ/agg Patented Nev. 4-, 1924.

UNETED STATES PATENT @FFICE.

LEROY D. KELLQGG, 0F DEERFIELD, ILLINOIS, ASSIGNOR T0 KELLOGG S'WITCHBOARD AND SUPPLY COMPANY, OF CHICAGG, ILLINOIS, A CORPORATION OF ILLINOIS.

TELEPHONE SYSTEYM.

Application filed January 30. 1922. Serial No. 532,640.

To all whom it may concern:

Be it known that I, LEROY D. KELLOGG, a citizen of the United States of America, and a resident of Deerfield, county of Lake, 2111C State of Illinois, have invented certain new and useful Improvements in Telephone Systems, of which the following is a specification.

My invention relates to automatic telephone systems, and particularly to private automatic exchange (P. A. systems employing preferably single level, spring-restored switches. Such a switch may have wipers on a rotary shaft, the shaft carrying a ratchet. A magnet having an arma ture with pawl to engage the ratchet drives the ratchet step by step, and so the wipers to engage successive contact sets in the arc-uate bank. I preferto have the ratchet driven on the back stroke of the armature. The customary off-normal contact-s are provided. Such a structure is shown in an application filed by Ernest A. Bohlman, January 3, 1922, Serial No. 526,532, and also shown in an application filed by William Kaisling, July 9, 1920, Serial No. 391,889.

Objects of the invention are to provide for conveniently increasing the capacities of such systems, and to provide certain novel and advantageous circuit systems. The latter are available for such increasing, but are not necessarily limited thereto.

Commonly used P. A. X. systems having switches with single level banks, are of the so-called adding type when the numbers of subscribers served are over ten. Such systems are familiar to those skilled in the art, and riefly the adding feature is occasioned by the ten-impulse maximum of the customary substation call dial. The multiple terminals of subscribers lines being in single groups in single level connector switch banks, if a called subscribers contacts are the fifteenth from the zero position of such a switch, the calling subscriber must operate his dial twice, say to its full capacity of ten impulses the first time, and a second time to transmit fiveimpulses more, when the switch will have traveled fifteen steps and be engaging the multiple contacts of the called line number fifteen. The calling subscriber then rings the called one by pressing a button.

in systems using single level switches, obviously with one pull of the dial the system is limited to ten subscribers, with two pulls to twenty, and so on, and the practical capacity of such a system is soon reached be cause of the increasing multiplicity of digit numbers to be pulled.

According to the present invention, first selectors are inserted between calling lines and the connectors carrying the called contacts of subscribers lines. These first selectors are single level bank switches and may be the same as the connectors mechanically, but have differently arranged controlling circuits.

The first selectors are of an adding type, as well as are the connectors, and adding type first selectors are believed to be new in the art.

In describing the present invention, a limit of four pulls of a subscribers dial will be assumed as the maximum permissible,

and this will give an exchange capacity of eighty subscribers as against forty in the present systems, using single level switches and employing the same numbers of dial pulls.

The eighty subscribers lines will preferably be divided into three groups as called lines; two of these groups will have thirty lines each and. the third will have twenty lines. The called multiple terminals of the lines of a particular group will appear in the banks of a certain number of adding type connectors assigned to that group. The terminal contacts of the first line of a group will at each connector be the contacts engaged when the connector makes its first step from normal, those of the second line will be engaged whenever a connector makes two steps from normal, and so on for the full number of lines in the group.

As a calling line each line may have its individual first selector in the shape of a switch with a single level bank containing, say, thirty sets of contacts. The first eight sets of contacts engaged by each first selector as it steps along its first eight steps from normal, may be multiple terminals of the eight connectors of the first group, the

contact sets ten to eighteen may be multiple terminals of nine connectors assigned to group two, the ninth contact set will be for a purpose hereafter explained and contact sets nineteen to thirty may be multiple terminals of connectors assigned to the third group.

7 plots.

On. the usual principle, a calling subscriber operates his dial to cause his first selector to select the group of terminals of connectors assigned to the line group in- .cludin g the called line; the first selector then be 1 and the calling subscriber will transmit one impulse to select the group. The first digit of each line inthe second group will be and the calling subscriber transmits ten impulses to select the group. The first two digits of lines of the third group will be 9.0. and the calling subscriber will transmit first nine impulses and then ten impulses to select the third group.

Referring now to Fig. 1, including parts 1 and 2, I have diagrammatically indicated two substations A and B of a well knonvn type, each having a call dial D and a ringing key K.

Each substation is connected with the exchange by line limbs LL, which terminate thereat in first selector circuits, those as sociated with substation A being shown comshown incomplete for lack of space, are in fact identical with those of A.

The first selector circuits, SEL, include a line relay LR to transmit impulses to motor magnet ll'lM, relay LR receiving the substation impulses direct. Motor magnet MM serves to directivel'yadjust wipers 22, 23, 2%, sole t a group and the said magnet also serves to adjust the wipers in their travel seekingidle connector contacts. RE is a combined release magnet and line cut-oil relay. The oil-normal contacts are indicatec at ll. The notion of relays 2, 3 and i can best be indicated in the narrative of oper ation. All apparatus is shown at normal.

The connector circuits at CONN include a pair or" line relays LR and LE the latter being differentially wound for purposes in dicated later. MM is the motor magnet;

.Oll indicates the oil-normal contacts; G

the ringing generator, and BB the'busy-back apparatus. ER is the release relay controlling release magnet RM' and CC and ST are control relays. The wipers are indicated at 429, an d 51 and multiple terminals olcalled line include each a contact 53, 54 and 55, these constitutinga set of called line contacts. Each connector isv connected to the first selector banks by its wires 31, 32, 33 and 34; terminating in said banks in multiple contacts 26, 27, 28 and 29, respectively. The

grouping of lines as called lines, the location and arrangement o1 the contact sets 53, 54, of called lines in the banks has hereinbcfore been indicated, as has the arran e Those for substation l3, although ment and location of the set s ot connector terminals 26, 27, 28, 29 in the first selector banks.

Fig. 2 shows a modification of my invention for giving the calling subscribers a busy signal in case all of the connector switches of a selected group are found busy.

[Vanna-Moe of operation.

moves his receiver and the switchhook contacts conductively unite line limbs LL, energizing relay LR by currentirom batt ry through the upper winding of LB, normal contacts 17 and 5', limbs L and L, normal contacts 8 and 20, lower winding of relay LR to ground. Relay LR closes alternate contact 16, energizing slow release relay 2-, it

being understood that all relay-s, indicated by the symbol at 2, are constructed so as to release their armatures slowly after they are deprived of current.

Relay 2 attracts armatures 9 and 10.. Subscriber at si-ibstation At now actuates dial D, so that in its return to normal it causes nine breaks and makes inthe circuit or relay LR, anc said relay d'eenergizes and energizes nine times, but so rapidly that relay 2 remains operated throughout; Each de-energizationof relay LR transmits a current impulse from. ground through normal contact 16, contacts 21 and 10 through motor magnet MM Theiirst energization of motor magnet Mil l operates slow release relay 3 bycurrent through contact It to ground at off normal contact @N. Relay 3. locks itself by contact -11 and remains operated during the nine vibrations'of 14 because of its slow release construction, thus holding contacts 12, 13 open. I

Fach de--energization of motor magnet MM advances wipers 22, 23, 24;, 25 aistep and on the first step off normal contact- ON disengages its normal contact and engagesrits alternate contact. At the end of the n ne actuations of motor mlagnet'hlM, wipers 22,

25, 24-, 25 will be engaging their ninth conto battery, c-ausingnine energizat'ions and de-energizations of magnet MM.

contacts 30, 30 and 30 will be left unwired, through magnet MM to energize it, but

while contact 30 will be permanently wired to battery through a non-inductive resistance, which may be individual to the first selector or common to three or tour selectors.

At the end of the nine impulses, relay LP remains energized and motor magnet MM tie-energized until the subscriber at substation A again operates his dial D, and contact 14 will be open during this time. Relay 3, however, is maintained energized in this interval by battery through resistance 7', contact 3023, through the said relay to ground at armature 11. Contacts 12 and 13 thus remain open and keep magnet MM disconnected from relay 4 to prevent a false operation of the system at this time.

The subscriber now operates his dial according to the 0 indication, which as usual causes ten breaks and makes in the substation circuit, and from the preceding it is ap parent that relay LR and motor magnet MM are effective to step wipers 22, 23, 24, ten

iore steps so that on the last step they will engage the nineteenth contact set, 26, 27 28, 29, in their bank. After wiper 23 disengages contact 30, the vibrating armature 14 keeps relay 3 operated until after the last step is made.

After the last step the substation circuit remains closed until the subscriber again operates his dial, and during this time 1'e lay LR is energized and magnet MM deenergized. There is no battery connected to the contact 27 now engaged by wiper 23, the relay 3 de-energizes and contacts 12 and 13 close.

It will be remembered that set 19 in the bank is the first setof multiple contacts connected to a connector of the third group out lines.

It the connector of thissetis idle, its contact 26 will be on open circuit, and it it is busy contact 26 will be connected directly to ground. Assuming first that it is busy, circuit is traced from battery through magnet MM, normal contacts 15, 7, 12, 19, wiper 22, contact 26, and over a direct low resistance connection to ground.

Magnet MM now energizes, attracts ar1nature 15, which de-energizes it, and thus steps the wipers to engage the second contact set of the third group. If this is busy the operation repeats and will continue until an idle set is encountered. During the stepping, relay 4- was connected with battery through magnet MM to ground at alternate contact of ofi normal contact ON via contacts 12 and 18, but said relay 4: was shortcircuited by the grounds via. contact 22-26 and did not receive enough current to operate. When wiper 22 engaged the idle, i. e., ungrounded, contact 26, relay 4 was no longer shunted and received enough current owing to the resistance of 1-, magnet MM does not energize at this time and the wipers remain at rest.

The closing of alternate contact 19 grounds the multiples of the selected connector, male ing it busy.

Armatures 17 and 19 disconnect relay LR and extend conductors L and L to wires 34 and 33, while 21 opens a contact in the circuit of magnet MM. Arn'iature 16 of relay LR- dropping back, de-energizes relay 2.

If the first contact set of the third group had been idle when switch SEL came to rest, engaging it, it is apparent that no energization-of magnet MM would have taken place, relay 4 would have had no short circuit to ground about it, and would thus have immediately energized in series with magnet MM, the latter remaining inert and the first connector of the third group would have been the one seized.

Substation A is now connected through to an idle connector CONN of the third group and the relays LR and LR energize over the calling line. Relay LR closing alternate contact 39 energizes relay RE, which. is of slow release construction. Relay LR energizes by its upper winding, and closes contact 37, energizing slow release relay CC, whose contact 41 energizes relay ST. Armature 38' closes the lower differential winding of relay LE to ground via alternate contact 39, but the upper winding of relay LR overpower-s the lower winding and the relay remains operated.

The subscriber now operates his dial according to digit 9, and nine interruptions of the substation circuit de-energize relays LR and LE nine times, and the nine times re tracted armature 39 energizes and de-energizes motor magnet MM nine times, since relay CC remains operated. The motor magnet MM accordingly steps wipers 19, 30, 51 nine steps from normal, wipers 59 and [it being on open circuit at 46 and 48.

Subscriber A now operates his dial ac cording to digit 8, and the connector steps ahead eight more steps, its wipers then engaging multiple contacts of the wanted line 9098.

Subscriber A now actuates ringing he K, which inserts resistance i into the line circuit. This reduces the current How in the upper winding of relay LE and in relay LR. The latter still gets enough current to remain operated, but the reduction in relay LR allows the lower winding to neutralize or slightly overbalancethe eiiect of the upper Winding and contacts 37, 38 open. The upper winding of relay LE is not of sutlicient power to re-operate the relay while N is in circuit, and the relay remains de-energized until the subscriber releases key K.

The opening of contact 37 tie-energizes relay CC, and the armature 41 shifts the connection of the already-energized relay ST from ground at 43 to the wiper 49,? Assuming first that the called line is idle, then; the contacts 53, 5.4, 55 will be connected as shown in full in Fig. 1, part 1, that is, contact 53 will be clear of ground and connected to the combined release magnet and cut-off relay RE. Under these circumstances relay ST of the connector receives no operating current and de-energizes, its armature 47 disconnecting it from wiper 49 and connecting relay AR to said wiper. Contacts 46 and 47 now establish the talking circuit.

Circuit is now traced as follows: From ground at alternate contact 39, through relay AR, normal contact 47, contacts 49, 53, normal contact 18'of the called line circuit (referring for convenience to Fig. 1, part 1 normal cont-act 9 and to battery through relay RE, of the called line. Relay AB of the connector and relay RE of the called line both energize, the latter cutting off the line relay LR- and by armatures 5 and 8 bridging talking battery across the called line through the inductive resistances shown. Attracted armature 43 of relay AR prevents a false release when subscriber A releases key K, and the ground through said relay AR connected to wiper 49 and contact 53. and its multiples places the called line in condition to test busy. Due to resistance P and construction of relays 4 and RE of called line, relay RE energizes first and opens circuit of relay 4. Contacts r are the eighth group of contacts, and contacts y the ninth group of contacts.

Generator G is now in circuit with the called substation to ring its call bell.

When subscriber A releases K, resistance N is cut out, relay LE energizes and in turn energizes relay CC, which by 40 completes the talking circuit, and as soon as subscriber B answers the ring, conversation. can proceed.

When at the end of conversation the subscribers replace their receivers, the act at B does not release any switch. The replacing at A, however, de-energizes both relays LR andv LE and relay LR opens the circuit of relay RR, whose de-energization re.- leases armature 45, which closes circuit through magnet RM andv relay ST via contact 3 6. The release magnet RM withdraws the usual retaining pawl, and relay ST places the wipers on open circuit, and the connector spring-restores to normal, whereby alternate contact of off normal contacts ON are shifted back to normal. In this conection it should beobserved that motor magnet MM will energize at the. time of release, but no stepping ahead of the connector will occur for this reason: relay ER is slightly quicker to release than relay CC in order that the release magnet RM may energize before relay CC de-energ'izes, and said magnet in withdrawing the. retaining pawl also draws the driving pawl of; motor magnet MM out of efiect-ive relation with the ratchet so that when motor magnet MM does de-energize, that is ineffective as to stepping. V

The releasemagnet, RM energizing connects ground: wire 32 through alternate con-- tact 41 of said ma et RM, circuit being now traced, over 32, 27, 23, alternate contact 18 and normal contact 9 to battery through, release magnet RE at switch SEL and due to the establishment of this circuit, said magnet RE energizes to Withdraw the retaining pawl of. the selector,'which spring restores, the wipers being open at contacts 5 and 8, and all apparatus is at zero as soon as ofinormal contacts ON shifts back to normal.

Called Zine busy.

If; at the time subscriber A depressed key K, the line wanted was busy as a calling line, its multiples 53 would be grounded at alternate contact of off-normal contacts ON,

or if busy as a called line, said multiples would be grounded from the wipers-of the connector already making it busy via that connectors relay AR to ground at its alternate contact 39.

In either case relay ST of the testing connectorwould remain. energized when it was busy as a calling line.

Having traced. a connection to completion in the. third group, which required the add,- ing function, of the selector which is not employed when the called line is in the first and secondv groups, the operationswhen the wanted line is in group one or two will be readily understood. For group 1, transmission of a single impulse places the selector in engagement with the first connector of group. one, and. he e eing vno sp cialcoir ta t 3Q tcln erfcre, e -10 i. n Kile-con- .nect r uld pr ed ex c ly s. de c ibed hereinbefore as of the time when the selector hadbeenconnected tocontact 19.

And so o he second gr up, he pulling of the dial according to digit 0 will step the firstselector ten steps, and so beyond the special contact 30 and selection of an idle connector of group 2 will, proceed as in the case of the group after th lli f a single digit, 1 r

The resistance P is inserted to pro- Considering the system as a whole, it is apparent that to reach the first ten subscribers in group one, a calling subscriber will transmit two sets of digit impulses, those subscribers being numbered from 11 to 19 and then 10. The first ten subscribers in the second group would also be reached by two sets of impulses, their numbers being from 01 to 09, followed by 00, and it is apparent that the second and third ten lines of groups one and two will be reached by the transmission of three and four digit impulse sets, respectively. The first ten lines of group 3 will be reached by the transmission of three digit impulse sets and the second ten lines of group three by four sets.

In a private automatic exchange with the ample provision of connectors for the difit'erent groups outlined above, taken in connection with the amount of traffic that experience shows occurs in such systems, it would be of extremely rare occurrence that a seeking selector would find all the connectors of a group busy. It the condition did exist, the calling subscriber would get a wrong number and would call again later.

However, by making the eighth, the eighteenth and the twenty-ninth contact sets in the first selectors non-multiple and connecting the contacts 28 and 29 of these sets as indicated in Fig. 2, the possibility suggested above may be avoided, at the sacrifice of one connector in each of groups 1 and 2. With the arrangement as shown in Fig. 2 (it being understood that the arrangement shown in Fig. 2, will replace the two middle contact banks of switch SEL) and in case an overrun occurs, subsequent impulse sets will simply interrupt the circuit of the slow release relay SR which, however, holds itself operated during their transmission, and also while the key K is operated. The subscriber hears the usual busy signal, replaces his receiver and the selector restores to normal in an obvious manner.

Groupings other than that hereinbefore suggested may be used. For example, but four connectors might be assigned to each group of lines, and with this number five groups could be selected by the selectors, two groups with one actuation of the dial and the other three groups with two actuations. Such an arrangement would increase the capacity afforded by four actuations of the dial to 120 subscribers, divided into two groups of 30 each and three groups of 20 each. This and other modifications will readily suggest themselves, and I do not wishi to be limited to the precise structures shown and described, but what I claim is:

1. A telephone system comprising subscribers lines divided into groups as called lines, adding type connectors divided into corresponding groups, adding type selectors operable in a single plane only for interconnecting calling lines with idle connectors of desired groups, and impulse mechanism for transmitting directive impulses to selectors and connectors.

2. A telephone system including subscribers lines divided into groups, connectors in corresponding groups for connecting directly to called lines, selectors operable in a single plane only for interconnecting calling lines with idle connectors of desired groups, adjusting apparatus for a selector, means for actuating said apparatus by a plurality of sets of digit impulses, said selector traveling in response to each set of said plurality, and apparatus automatically Serving to cause said selector to pick out an idle connector after the transmission of the. last impulse sets.

3. A selector for automatic exchanges or the like comprising contact sets in a. single level on the selector bank, contact makers for said selector adjustable responsive to a plurality of sets of digit impulses, a single driving magnet for adjusting said contact makers, and automatic seeking mean operative after the transmission of the last set of said plurality to select an idle set of contacts in said level.

4:. A selector for automatic exchanges or the like including contact sets arranged in groups in a single level on the selector bank, directive impulse transmitting and receiving means including a single driving magnet to adjust the selector to select various groups, automatic selecting mechanism including said driving magnet for the selector operative to cause it to pick out an idle cont-act set of the selected group, said mechanism effeotive to initiate its operation under one condition after transmission of one set of directive impulses and under another condition after the transmission of a plurality of sets of impulses.

5. A selector for automatic exchanges having a bank with contact sets arranged in groups, digit impulse transmitting mecha nism, means for causing automatic selection by said selector of idle contacts of selected groups, electromagnet apparatus including a single driving magnet for the selector to receive the digit impulses and adjust said selector in response thereto, said selector selecting certain groups responsive to a single digit impulse set and others in response to a plurality of digit impulse sets, and a, special contact set preventing initiation of said automatic selection between the transmission of certain digit impulse sets.

6. An adding type selector including contact sets and mechanism including a single driving magnet responsive to digit impulses to select groups of said contact sets and then automatically an idle set of the selected group, apparatus for initiating the automatic selection after a group has been seselection after a group has been selected in response to a plurality of digit impulse sets.

7 A selector for automatic exchanges or the like comprising a plurality of contact sets arranged in groups on theselector bank, mechanism including a single driving magnet responsive to digit impulses to select groups of contact sets and then automatically anidle set of the selected group, apparatus for initiating such automatic selection in some cases after transmission of one digit impulse set, and means for preventing such initiation in other cases after one impulse set and causing such initiation after a plurality of digit impulse sets are transmitted.

8. An automatic telephone system comprising telephone lines divided into groups as called lines, connectors, including multiple terminals of said lines, arranged in corresponding groups, directive impulse adjustingoapparatu for a connector operative to connect. With terminals of some of said lines in response to the transmission of a single digit impulse set, and vvith terminals of other lines in response to the transmission of a plurality of digit impulse sets, selectors operable in a single lane only, multiple terminals of said connectors-at said selectors arranged in groups, directive impulse adjusting mechanism for a selector operative to select a certain group of said terminals in response to the transmission of a single digit impulse set, and another group in response to the transmission of a plurality of digit impulse sets, and mechanism for the selector to enable it to select idle' contacts of a selected group of terminals automatically 0perative after the selection of the group. 7

Signed by me at Chicago, in the county of Cook and State of Illinois, this 27 day of January, 1922. r V

LEROY D. KELLOGG. 

